1. Field of the Invention
This invention relates to a method of cleaning reticles for use in conjunction with the fabrication of semiconductor devices.
2. Brief Description of the Prior Art
In the manufacture of semiconductor devices, a plurality of reticles are generally required with each reticle providing the basic pattern for each level of the semiconductor device. A problem generally arises whereby contamination or particles are deposited on the reticle and thereby causes a pattern somewhat different from the intended pattern to be formed on the semiconductor device. In fact, with the continued miniaturization of semiconductor components in integrated circuits, often a speck of dirt from the air which may be too small to be noticed can land on the reticle and cause a fatal defect in the finally fabricated device such as, for example, a short circuit or an open circuit
In order to avoid the above described problem, the reticles have been stored in boxes. When required, the reticle is removed from the box and inspected under very bright light to determine whether specks of dirt were contained on the reticle. The dirt was then blown off of the reticle using a nitrogen gun. This involved holding the reticle and attempting to maintain the reticle clean while also blowing off any dirt contained on the reticle. The reticle was then replaced in the box. An additional optional step included cleaning out of the box with the nitrogen gun to minimize the possibility of contamination of the reticle within the box itself. The reticles were then stored in the boxes in a reticle library which is a closed clean container. When required to be used, the reticles are removed from the boxes in the reticle library, entered into a stepper where they are used to form one or more patterns during processing of a semiconductor device and are then returned to the box in the reticle library.
It is apparent that it desirable to maintain the reticles as clean as possible, with cleanliness being enhanced by removal of the human handling factor to the greatest extent possible.